Postoperative pulmonary complications (PPCs) often lead to increased patient morbidity and mortality, hospital length of stay and resource utilization. As many as 35 risk factors associated with PPCs have been identified. Yet little has been done to systematically develop the list of risk factors into a practical predictive model for clinical use. A model building study will be used to prospectively examine individual risk factors associated with the development of a PPC in subjects undergoing an abdominal surgical procedure. Risk factors which are accessible to the nurse in the preoperative, intraoperative and immediate postoperative setting will be used. These risk factors will be used in the development of a predictive model for PPCs and the model will be tested in an independent sample. Three institutions will be used for data collection and the target population is adults who will undergo a scheduled abdominal surgical procedure. A sample size of 540 is projected over the course of 14 months. A multi-criteria outcome of PPC will be used and 16 risk factors will be assessed:age, sex, smoking history, body mass index, mobility, level of consciousness, length of stay prior to surgery, history of lung disease, history of other disease(s), preoperative respiratory therapy, anesthesia risk, duration of anesthesia, location and type of surgical procedure, incision direction and nasogastric tube. Logistic regression analysis will be used to examine the risk factors for univariate effects on PPC and to develop the multivariate model. A split sample technique will be used to test the predictive model. The sensitivity and specificity of the model will be assessed.